1. Field
Embodiments of the present invention relate to a semiconductor technology, and more particularly, to a variable resistance memory device and a method for fabricating the same.
2. Description of the Related Art
Recently, a variety of variable resistance memory devices have been developed. The term “variable resistance memory device” refers to a device which stores data using a variable resistance material switching between different resistance states depending on an applied bias.
A variable resistance memory device in which switching occurs due to a filament serving as a kind of current path that is locally created/destroyed in a variable resistance material layer formed of metal oxide is referred to as ReRAM (Resistive Random Access Memory). Because the creation/destruction of the filament occurs according to the behavior of oxygen vacancies within the metal oxide in certain devices, the variable resistance material layer in such devices must have a layer including oxygen vacancies.
Specifically, the variable resistance material layer may include a double layer of an oxygen-deficient metal oxide layer containing oxygen at a lower ratio than a stoichiometric ratio, and thus including a large quantity of oxygen vacancies, and an oxygen-rich metal oxide layer satisfying the stoichiometric ratio. The oxygen-deficient metal oxide layer supplies oxygen vacancies to the oxygen-rich metal oxide layer, and the oxygen-rich metal oxide layer corresponds to a layer in which a filament is created or destroyed depending on whether or not oxygen vacancies are introduced from the oxygen-deficient metal oxide layer, and switching occurs.
The double layer may have a structure in which the oxygen-deficient metal oxide layer is positioned at the bottom and the oxygen-rich metal oxide layer is positioned at the top, or vice versa.
However, when the oxygen-rich metal oxide layer is positioned over the oxygen-deficient metal oxide layer, a part of the oxygen-deficient metal oxide layer may be oxidized during deposition of the oxygen-rich metal oxide layer. In this case, oxygen vacancy density may decrease, and thus the switching characteristics may be degraded.